To learn about Bitcoin technical aspect I recommend this material.
https://github.com/bitcoinbook/bitcoinbook#chapters

When dealing with Bitcoin you'll realize how important privacy and security is, so I'd recommend the following links to help you learn more about them.
https://www.lopp.net/bitcoin-information/security.html

You can still use this site to learn more about Bitcoin.
https://coindesk.com/learn
https://learnmeabitcoin.com/
https://www.bitcoin.com/get-started/

Another material that I have used in the past most especially when I was new to the forum was: Beginners & Help Encyclopedia
It's has some materials already arranged for you, it's not only for Bitcoin though.